Disposable diaper

ABSTRACT

A disposable diaper has a through-hole formed in an inner sheet destined to come in contact with a wearer&#39;s skin so that this through-hole may communicate with a pocket for receiving feces. The inner sheet is formed with an elastic area extending in a longitudinal direction along transversely opposite side edges of the through-hole. In a crotch region of the diaper, a stiffening sheet strips are attached to the inner sheet between the transversely opposite side edges of the diaper and the transversely opposite side edges so that the respective stiffening sheet strips extend in a transverse direction.

BACKGROUND OF THE INVENTION

The present invention relates to disposable diapers having a meansadapted for receiving feces.

There has already been proposed disposable diapers having a pocket as ameans adapted for receiving feces, comprising a first sheet facing awearer's skin and a second sheet facing the wearer's garment wherein, ina crotch region of the diaper, the first sheet is formed with athrough-hole communicating with the feces receiving pocket definedbetween the first and second sheets so that the through-hole may bealigned with anus of the wearer when the diaper is put on the wearer'sbody.

For example, U.S. Pat. No. 4,990,147 (Citation 1) discloses a disposablediaper comprising a liquid-impervious backsheet, a liquid-pervious linerand a bodily waste absorbent core interposed between the backsheet andthe liner. The liner is formed with a through-hole adapted to guidefeces therethrough toward the core and thereby to protect the wearer'sskin from being contaminated with feces. The liner is formed at leastpartially by an elastic panel serving to keep a periphery of thethrough-hole in close contact with an area surrounding the anus. In thisdiaper, a stock material for the elastic panel may be selected from thegroup consisting of a nonwoven fabric of a polyurethane elastic threadsand a knitted fabric of inelastic threads.

WO 03/009795 A1 (Citation 2) discloses a disposable diaper asillustrated in FIGS. 8 and 9 of the accompanying drawings wherein FIG. 8illustrates the diaper in its elastically stretched state and FIG. 9illustrates the diaper in its elastically contracted state. The knowndisposable diaper comprises a backsheet 126 and a topsheet 124 formedwith a slit-type opening 130 allowing feces to pass therethrough so thata pocket serving for receiving feces may be defined between the top- andbacksheets 124, 126. Along a pair of transversely opposite side edges ofthe slit-type opening 130, elastic bands are bonded in stretched statesto the topsheet 124 so as to form elastic areas 131, 132 extending inparallel with the center line X in a longitudinal direction. The elasticarea 131 is contiguous to an elastic area 143 obliquely extending towarda front waist region so as to draw apart gradually from the center lineX, on one hand, and to an elastic area 145 obliquely extending toward arear waist region so as to draw apart from the center line X, on theother hand. In the similar manner, the elastic area 132 is contiguous toan elastic area 144 obliquely extending toward the front waist region soas to draw apart gradually from the center line X, on one hand, and toan elastic area 146 obliquely extending toward a rear waist region so asto draw apart gradually from the center line X, on the other hand. Theelastic areas 131, 143, 145 cooperate with the elastic areas 132, 144,146 opposed to the areas 131, 143, 145 to define a generally X-shapedelastic zone. The slit-type opening 130 may be positioned in alignmentwith the anus when the known diaper is put on the wearer's body.

The liner of the diaper disclosed in Citation 1 as well as the topsheetof the diaper disclosed in Citation 2 may be formed from the elasticsheet. One example of such elastic sheet is a nonwoven fabric of elasticthreads such as polyurethane elastic threads, which falls, however, intodisfavor with wearer's mothers due to uncomfortable rubber-like touchpeculiar to this nonwoven fabric. The other example of such elasticsheet is knitted fabric of inelastic threads, which is, however, toocostly to be used for the disposable diaper. For the diaper disclosed inCitation 2, the elastic threads may be attached to the nonwoven fabricof inelastic threads to ensure that this nonwoven fabric is partiallyelasticized. The topsheet formed from a nonwoven fabric made ofinelastic threads and partially elasticized in this manner certainlysolves the problem that the wearer might experience uncomfortablerubber-like touch so far as the diaper is in the state as shown in FIG.8. However, in response to elastic contract of the elastic bands, awidth W of the slit-type opening is varied and simultaneously the crotchregion is formed with a plurality of irregular and outstandingcorrugations 150. Variation occurring in the width W of the slit-typeopening makes it difficult to position the side edges of the slit-typeopening in alignment with the both lateral sides of the wearer's anus.Such instable width of the opening must be alleviated by minimizing thewidth W of the opening and covering the wearer's skin with the topsheetin the vicinity of the diaper wearer's anus so that the wearer's skinmay be protected from being contaminated over a wide range. Formation ofa plurality of corrugations prevents the topsheet from being kept inclose contact with the wearer's skin, resulting in that bodily waste mayleak out beyond the periphery of the slit-type opening and/or appearanceof the diaper put on the wearer's body may be damaged. It is a principalobject of the present invention to improve the disposable diaper ofprior art so that the problems as have been described just above may bereliably solved.

SUMMARY OF THE INVENTION

The present invention is directed to a disposable diaper comprising achassis having a crotch region, a front waist region extending forwardfrom the crotch region and a rear waist region extending rearward fromthe crotch region, and a liquid-absorbent panel interposed between afirst sheet defining an inner surface of the chassis and facing awearer's skin and a second sheet defining an outer surface of thechassis and facing the wearer clothes. The first sheet being spaced, ina transversely middle zone of the crotch region, from the second sheetas well as from the body fluid absorbent panel in a thickness directionof the first sheet to define a pocket adapted to receive feces, thefirst sheet being formed along a center line bisecting a width of thecrotch region with a through-hole extending in a longitudinal directiontoward the front waist region and the rear waist region, respectively,in communication with the pocket, the through-hole being provided alongits transversely opposite side edges extending in parallel to each otheron both sides of the center line with elastic members attached instretched states to the first sheet. The elastic members respectivelycomprise intermediate sections extending in the longitudinal directionalong the transversely opposite side edges of the through-hole andsections extending from the intermediate sections so as to be graduallyspaced away from the center line.

The diaper according to the invention further comprises the first sheetin the crotch region being formed between the transversely opposite sideedges of the diaper extending in the longitudinal direction and thetransversely opposite side edges of the through-hole with a meansadapted for locally enhancing a flexural stiffness of the first sheet inthe transverse direction of the diaper so as to restrict a deformationof the first sheet in the transverse direction.

According to one preferred embodiment of the invention, the restrictingmeans are formed intermittently in the longitudinal direction.

According to another preferred embodiment of the invention, therestricting means are formed from bonding sheet strips preparedseparately of the first sheet to the first sheet.

According to still another preferred embodiment of the invention, therestricting means are formed by coating the first sheet with hot meltadhesive.

According to still another preferred embodiment of the invention, thefirst sheet comprises a nonwoven fabric of thermoplastic syntheticfibers and the restricting means comprise film-like spots formed bylocally melting and solidifying the nonwoven fabric.

According to further another preferred embodiment of the invention, therestricting means comprise corrugations of the first sheet regularlyundulating in the longitudinal direction.

The first sheet has a flexural stiffness in the transverse direction ofthe diaper locally enhanced to define means adapted to restrain adeformation of the first sheet in the transverse direction of thediaper. This unique arrangement is effective to prevent the first sheetin the crotch region from significantly shifting in the transversedirection of the diaper and thereby to prevent the width between theside edges from being significantly varied even under elasticcontraction of the elastic members extending in parallel to the centerline along the side edges of the opening formed in the crotch region ofthe first sheet and then obliquely extending toward the front and rearwaist regions so as to draw apart gradually from the center line.

The means adapted to restrain a significant deformation of the firstsheet include bonding of sheet strips prepared separately of the firstsheet to the first sheet intermittently in the longitudinal direction,forming the first sheet with a plurality of hot melt adhesive coatedareas intermittently in the longitudinal direction of the diaper whereineach of these areas extends in the transverse direction of the diaper,forming film-like spots prepared by melting and solidifying the nonwovenfabric, and forming the first sheet with a plurality of gathersundulating in the longitudinal direction of the diaper.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially cutaway plan view showing the disposable diaperaccording to a typical embodiment of the present invention in itselastically stretched state;

FIG. 2 is a sectional view taken along the line II-II in FIG. 1;

FIG. 3 is a sectional view of an inner sheet taken along the lineIII-III in FIG. 1;

FIG. 4 is a view similar to FIG. 3, showing one preferred embodiment ofthe invention;

FIG. 5 is a view similar to FIG. 3, showing another preferred embodimentof the invention;

FIG. 6 is a view similar to FIG. 3, showing still another preferredembodiment of the invention;

FIG. 7 is a view similar to FIG. 3, showing further another preferredembodiment of the invention;

FIG. 8 is a partially cutaway plan view showing the diaper of prior artas its elastically stretched state; and

FIG. 9 is a perspective view showing the diaper of FIG. 8 in itselastically contracted state.

PREFERRED EMBODIMENTS OF THE INVENTION

Details of a disposable diaper according to the present invention willbe more fully understood from the description given hereunder withreference to the accompanying drawings.

FIG. 1 is a partially cutaway plan view showing the disposable diaper 1according to a typical embodiment of the present invention. The diaper 1is illustrated herein as has been elastically stretched in alongitudinal direction Y corresponding to a vertical direction as viewedin FIG. 1 as well as in a transverse direction X. As viewed in thelongitudinal direction Y, the diaper 1 has a crotch region 6 lying in amiddle zone, a front waist region 7 extending forward from the crotchregion 6 and a rear waist region 8 extending rearward from the crotchregion 6. The diaper 1 further includes a chassis 2 which is rectangularin FIG. 1 and provided with a pair of front wings 11 respectivelyextending outward from transversely opposite side edges 3 of the chassis2 in the front waist region 7 and a pair of rear wings 12 respectivelyextending outward from the transversely opposite side edges 3 in therear waist region 8. The rear wings 12 are provided with tape fasteners13 which are, in turn, formed on respective inner surfaces withpressure-sensitive adhesive areas 14.

The chassis 2 is contoured by the transversely opposite side edges 3extending in the longitudinal direction Y of the diaper 1 and front andrear ends 16, 17 extending in the transverse direction X correspondingto a width direction of the diaper 1. The chassis 2 has an inner sheet22 to contact with a wearer's skin and an outer sheet 23 to contact withthe wearer's garment. The inner sheet 22 is formed with an oblongthrough-hole 26 extending in the longitudinal direction Y on the centerline C-C bisecting a width of the diaper 1 so that a bodily wasteabsorbent panel 24 interposed between the inner and outer sheets 22, 23may be seen through this through-hole 26. A periphery of thethrough-hole 26 is defined by a pair of transversely opposite side edges31 extending in the longitudinal direction Y generally in parallel tothe center line C-C, a front edge 36 generally describing a V-shape anda rear edge 33 generally describing an inverted V-shape. Front and rearbands 28, 29 both extending in the transverse direction X are attachedto a surface of the inner sheet 22 facing the wearer's skin along thefront and rear ends 16, 17, respectively. The inner sheet 22 furtherincludes elastic areas 40 comprising intermediate sub-areas 36 extendingalong the transversely opposite side edges 31 of the through-hole 26generally in parallel to the center line C-C, front sub-areas 37obliquely extending from the vicinity of the front edge 32 of thethrough-hole 26 toward the front band 28 so as to draw apart graduallyfrom the center line C-C and rear sub-areas 38 obliquely extending fromthe vicinity of the rear edge 33 of the through-hole 26 toward the rearband 29 so as to draw apart gradually from the center line C-C.

FIG. 2 is a sectional view taken along the line II-II corresponding tothe center line D-D bisecting a dimension of the diaper 1 in thelongitudinal direction Y. The inner and outer sheets 22, 23 are put flatand attached together using an adhesive means or a welding means alongthe transversely opposite side edges 3 as well as along the front andrear ends 16, 17 (See FIG. 1). Along the transversely opposite sideedges 3, leg-surrounding elastic members 41 are interposed between theinner and outer sheets 22, 23 and bonded in stretched states to at leastone of these sheets 22, 23 by means of hot melt adhesive (not shown) soas to extend in the longitudinal direction Y. The bodily waste absorbentpanel 24 interposed between the inner and outer sheets 22, 23 comprisesa core 42 formed from a mixture of fluff pulp and super-absorbentpolymer particles or of fluff pulp and super-absorbent polymer fibers,in any case, wrapped with a sheet 43 such as a tissue paper and/or anonwoven fabric. The bodily waste absorbent panel 24 is bonded to theouter sheet 23 by means of hot melt adhesive 45 (See FIG. 2). The innersheet 22 is left free from the outer sheet 23 and the bodily wasteabsorbent panel 24 except the side edges 3 and the front and rear ends16, 17 along which the inner sheet 22 is attached to the outer sheet 23so that a pocket 46 adapted for receiving of feces may be formed betweenthe inner and outer sheets 22, 23. The through-hole 26 of the innersheet 22 is in communication with this pocket 46 and adapted to guidefeces and/or urine into the pocket 46. In the vicinity of thetransversely opposite side edges 31 of the through-hole 26, elasticbands 48 are bonded in stretched states to a surface 47 of the innersheet 22 facing away from the wearer's skin by means of hot meltadhesive (not shown) so as to form the elastic areas 40. Furthermore, aplurality of stiffening sheet strips 51 (See FIG. 1) each extending inthe transverse direction between each of the elastic area 40 and each ofthe side edges 3 are attached to the surface 47 facing away from thewearer's skin using an adhesive or a welding means. These stiffeningsheet strips 51 locally enhance stiffness of the inner sheet 22 toalleviate a tendency that the inner sheet 22 might be formed withgathers as the elastic areas 40 are stretched and contracted in thelongitudinal direction Y and thereby prevent the width of the innersheet 22 as defined between the respective side edges 3 of the diaper 1in the crotch region 6 and the respective side edges 31 of thethrough-hole 26 from being reduced in a direction indicated by an arrowP due to formation of the gathers. In other words, the width W betweenthe side edges 31, 31 of the through-opening 26 is not significantlyvaried even when each of the elastic areas 40 is stretched andcontracted and, therefore, the width W is maintained substantiallyconstant before and after the diaper 1 is put on the wearer's body. Inthis way, both of the side edges 31 can be reliably positioned in thevicinity of the anus as the diaper 1 is put on the wearer's body. Sincethe stiffening sheet strips 51 are attached to the inner sheet 22 in thecrotch region 6 so as to be arranged intermittently in the longitudinaldirection Y and do not prevent the elastic areas 40 from contracting inthe longitudinal direction, the stiffening sheet strips 51 allow theinner sheet 22 to be formed between each pair of the adjacent stiffeningsheet strips 51 with a plurality of gathers which are relatively long inthe transverse direction X and repetitively undulating in thelongitudinal direction. In the crotch region 6 of such diaper 1 thegathers tend to be arranged in an orderly way in the crotch region 6 andpresent a good appearance when the diaper 1 is put on the wearer's body.

Of the diaper 1 constructed as has been described above, the inner sheet22 is formed from a liquid-pervious inelastic nonwoven fabric, a wovenfabric, a plastic film or the like. The outer sheet 23 is formed from aliquid-impervious, more preferably, liquid-impervious but breathablewoven fabric, a nonwoven fabric, a plastic film or the like. The elasticbands 48 may be of natural or synthetic rubber and have widths in arange of 2 to 20 mm. The front and rear bands 28, 29 are optionally usedto prevent the front and rear waist regions 7, 8 from being contractedin the transverse direction under the effect of the stretched elasticbands 48. These front and rear bands 28, 29 may be formed from anonwoven fabric having a basis weight in a range of 30 to 400 g/m², aflexible and elastic foamed plastic sheet or the like. The through-hole26 of the inner sheet 22 has a preferable dimensions, depending on thesize of the diaper, to have the widths W ranging from 10 to 70 mm and alength sufficient to cover the anus and the urethral of the wearer.

FIG. 3 is a sectional view of an inner sheet 22 taken along the lineIII-III in FIG. 1. Each of the stiffening sheet strips 51 attached tothe surface 47 of the inner sheet 22 facing away from the wearer's skinmay be formed from a woven fabric, a nonwoven fabric, a plastic film, aflexible and elastic foamed plastic sheet or the like having a dimensionin the transverse direction X of the diaper 1 less than a distance fromthe associated side edge 3 to the associated elastic band 48 (seeFIG. 1) and dimensions in the longitudinal direction Y in a range of 2to 20 mm. A distance between each pair of the adjacent stiffening sheetstrips 51 is preferably in a range of 2 to 50 mm.

FIG. 4 is a view similar to FIG. 3, showing preferred embodiments of theinvention. In the case illustrated in FIG. 4, the stiffening sheetstrips 51 are replaced by strips of hot melt adhesive 60 coated on theinner sheet 22 so as to extend in the transverse direction X. In thecase illustrated in FIG. 5, the stiffening sheet strips 51 are replacedby film-like areas 61 formed intermittently in the longitudinaldirection by locally melting and solidifying the inner sheet 22 made ofthe nonwoven fabric of thermoplastic synthetic fibers. These film-likeareas 61 extend in the transverse direction X of the diaper 1 as in thecase of the stiffening sheet strips 51 and have a stiffness higher thana stiffness of the nonwoven fabric left not melted to the film-likecondition between each pair of the adjacent film-like areas 61. In thecase illustrated by FIG. 6, the inner sheet 22 is formed with aplurality of gathers 62 regularly undulating in the longitudinaldirection Y. Crests and troughs of these gathers 62 provide a functionsimilar to those provided by the stiffening sheet strips 51 and thefilm-like areas 61. Finally in the case illustrated by FIG. 7, the innersheet 22 is formed with a plurality of gathers 62 which are thencollapsed so that the inner sheet 22 is bonded to itself using anadhesive means or a welding means in areas 66 in which the inner sheet22 is placed upon itself.

The present invention allows the disposable diaper having the pocket forreceiving feces to be improved so that the width of the through-openingcommunicating with the pocket can be substantially maintained constanteven when the elastic members attached to the inner sheet of the diaperin stretched states are left to contract.

1. A disposable diaper comprising: a chassis having a crotch region, afront waist region extending forward from said crotch region and a rearwaist region extending rearward from said crotch region; aliquid-absorbent panel interposed between a first sheet defining aninner surface of said chassis and facing a wearer's skin; a second sheetdefining an outer surface of said chassis and facing said wearer'garment; said first sheet being spaced, in a transversely middle zone ofsaid crotch region, from said second sheet as well as from said bodyfluid absorbent panel in a thickness direction of said first sheet todefine a pocket adapted to receive feces, said first sheet being formedalong a center line bisecting a width of said crotch region with athrough-hole extending in a longitudinal direction toward said frontwaist region and said rear waist region, respectively, in communicationwith said pocket, said through-hole being provided along itstransversely opposite side edges extending in parallel to each other onboth sides of said center line with elastic members attached instretched states to said first sheet wherein said elastic membersrespectively comprise intermediate sections extending in saidlongitudinal direction along said transversely opposite side edges ofsaid through-hole and sections extending from said intermediate sectionsso as to be gradually spaced away from said center line; and said firstsheet in said crotch region being formed between said transverselyopposite side edges of said diaper extending in the longitudinaldirection and said transversely opposite side edges of said through-holewith a means adapted for locally enhancing a flexural stiffness of saidfirst sheet in the transverse direction of the diaper so as to restricta deformation of said first sheet in said transverse direction.
 2. Thedisposable diaper according to claim 1, wherein said restricting meansare formed intermittently in said longitudinal direction.
 3. Thedisposable diaper according to claim 1, wherein said restricting meansare formed by bonding sheet strips prepared separately of said firstsheet to said first sheet.
 4. The disposable diaper according to claim1, wherein said restricting means are formed by coating said first sheetwith hot melt adhesive.
 5. The disposable diaper according to claim 1,wherein said first sheet comprises a nonwoven fabric of thermoplasticsynthetic fibers and said restricting means comprise film-like spotsprepared by locally melting and solidifying said nonwoven fabric.
 6. Thedisposable diaper according to claim 1, wherein said restricting meanscomprise corrugations of said first sheet regularly undulating in saidlongitudinal direction.
 7. The disposable diaper according to claim 2,wherein said restricting means are formed by bonding sheet stripsprepared separately of said first sheet to said first sheet.
 8. Thedisposable diaper according to claim 2, wherein said restricting meansare formed by coating said first sheet with hot melt adhesive.
 9. Thedisposable diaper according to claim 2, wherein said first sheetcomprises a nonwoven fabric of thermoplastic synthetic fibers and saidrestricting means comprise film-like spots prepared by locally meltingand solidifying said nonwoven fabric.
 10. The disposable diaperaccording to claim 2, wherein said restricting means comprisecorrugations of said first sheet regularly undulating in saidlongitudinal direction.